Landing and traffic control system



MalCh 17, 1959 A. M. cAsABoNAl A 2,878,469

LANDING AND TRAFFIC CONTROL SYSTEM 10 Sheets-Sheet 1 Filed Oct. 30. 1955 INVENTOR AA/rHoA/y M. CAsABo/VA ATTORNEY I March 17, 1959 10 She'ets-Sheet 2 N w T m m k j@ n o. w O

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Filed Oct. 30. 1953 ATTORNEY March 17, 1959 A. M. cAsABoNA LANDING AND TRAFFIC CONTROL SYSTEM 10 Sheets-Sheet 5' Filed oct- :5o.y 1953 mww Y au@ INVEN-roR Mfr/,romy M. @quam/,4

ATTORNEY March 17, 19.59 A. M. cAsABoNA LANDING AND TRAFFIC .CONTROL SYSTEM 1o sheets-sheet 4 Filed Oct. 30, 1953 INVENTGR wmvrvwxsnaama;

am' A 'woRNEY AMAN March 17, 1959 A. M. cAsABoNA 2,878,469 I LANDING AND TRAFFIC CONTROL SYSTEM Filed oct. :5o.v 1955 y 10'( Sheets-Sheet 5 MASTER 'staf AVA/c6 Barron/5 79 SLOT C sLoT n SL01' E,

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masa BY A ATTORNEY A. M. lCASABONA 'LANDING mn TRAFFIC CONTROL SYSTEM l0 Sheets-Sheet 6 nmwnw. E( om `INVENTOR WHO/vr /fz 0454504@ ATTORNEY EN 2m o no.

March v'117, 212959 Filed 001,. 530. 11953 y A. M. cAsABoNA 2,878,469

LANDING AND TRAFFIC CONTROL SYSTEM 10 y'Sheets-Sheet 7 March 17, 1959 Filedocvt. 3o. l195s March 17, 1959 A. M'. CASABONA.

LANDING AN@ CONTROL SYSEEMT I@ Sheetshheet &

Filed Oct. 50. 1953 A. GQ mkmm INVENTR Ammo/vr M A sAo/YA ATTORNEY Marchl7, 1959 A. M. cAsABONA 2,878,469

LANDING AND TRAFFIC CONTROL SYSTEM Filed 06,12. 50, 1953 10 Sheets-Sheet 9 AL 7'/ TUDE' SPEEa aR/VE 5R05# /07 /06 /09 //0 /l/ Il? ALERT :Tack GAT:

March 17, 1959 A. M. cAsABoNA 2,878,469 LANDING AND TRAFFIQ CONTROL sys-TEM Filed oct. 5o,4 1953 REMY Fal? 540'/ EACH COA/MCT REPRISE/V725' A 60A/MCT 6R05 @070k y l 1.- 2L l 1 M3 M4 I INVENTR wf/fom M. CAS/150444 ATTORNEY United States Patent ,LANDINGAND .TRAFFIC CONTROL SYSTEM Anthony Casabona, North `White Plains, N. Y., as- `signor to International Telephone'and Telegraph'Corporation, ;.Nutley, N. I., .a1/.corporation of Maryland Application ctober'30','1953, Serial No. 339,194 15 Claims. .(Cl. 343-112) This invention relates toa landing and tratiic control system vfor aircraftand more particularly to a .landing system Vand integrated ,traic control .system providing forthe orderly radio aided landing ofa large number of aircraft simultaneously approaching a given landing strip.

It is appreciated by all authorities on aircraft operations .that a well organized traffic control .system is a necessity vfor the proper and efficient utilization of any radio aid landing system. At present when a large number of aircraft approach .a .landingfield it is necessary to delay the arrival of the planes .so that the radio aids are not saturated .beyond 'their capacity. This delay causes the planes to circle around the landing strip or some designated rendezvous point. In bad weather when the capacityv ofany landing system is reduced the number of planes that can be'landed in any given time is greatly decreased andthe additional delay in landing causes the planes to stack up while awaiting their turn to utilize the landing facilities. This stack time is very costly and causes great inconvenience to air travellers. Any system which 'reduces stack time would be greatly appreciated by the air transport industry. `In addition to the ytime delay, Ypresent-day procedure requires that the airport control tower or landing control personnel'radio verbal instructions regarding the .stack location and thelocation of the individual plane within the stack to the pilot. The pilot must'then conform to these verbal instructions. In the interest of safety it is desirable to avoid verbal instructions, and this Ais particularly true in areas .of j-great traffic density such as occur when air tratic utilizing alanding strip must be stacked.

Perhaps the ultimate problem posed for a landing and vtraffic control system is .present aboard yan aircraft carrier when its planes return from a mission and desire to land. The number of aircraft approaching the carrier in such a situation .may be approximately a hundred or more. A t present'all carrier aircraft performthe functionof. homing to thecarrier orto a rendezvous point before considering'landing procedure. This results in the concentration of traffic in some small area with its'associated danger of collision. It is readily understandable that information about a'hundred aircraft is not comprehensibleto'one'individual in the short time Vnecessary for him 'to'make the arrangements for landing'nor-can a 'group' of "individuals assigned to certain sectors rapidly arrange the traic among themselves in thebest possible manner in the short time required.

It'is an object of 'this invention, therefore, to provide a landing and traic ycontrol system for Yaircraft vwhich is automatic in-its operation'and capable of controlling vla large number of aircraft.

It is another yobject ofthis invention to provide an automatic 'computer to control'the vapproach Yof a large number Yof'aircrafttoa landing strip equipped'with radio aidsfor landing.

AA Efurther object vofthis-invention `is toprovide van ice automatic traic controlsystem to allow for the .speedy and eliicient landing of a large number ofzairplanes with a minimumamount of .human supervision.

`A feature of vthis invention providingfor thelanding of aflarge number of .aircraft inaminimum of time .is the .traffic control provision whereby the .planes approach the landing area in an orderly .sequencerather .thanin groups. A computer issues commands to the individual aircraft to ya course in .order .to arrive at .the'landing site in the optimum sequence. The traiiic control and landing operation is controlled through .the use of .a stacksynchronized with a regular landing interval. Individual aircraft are controlled from an approach gate at vsome distance from the landing strip such :that .they each approach a previously assigned position inthe lsyn-A chronized stack. The aircraft orbits in the. synchronized stack until it intercepts a landing gate at which time itreceivesl theradio aid landing information to .guideit on its final approach leg.

YThe above-mentioned and other features and objects of this invention will become more apparent byreference to the following description taken in conjunction with the accompanying drawings, in which:

Fig. l is a schematic illustration of the landingstack configuration centered about an aircraft carrier;

Fig. 2 is a schematic diagram o'f the landing stack configuration of this invention;

Fig. 3 is a schematic diagram of the initiation of the landing stack configuration at a given. instant of time.

Figs. 4 and 5 are schematic illustrations of the .landing stack of Fig. 3 thirty seconds and ninety `seconds later respectively;

Fig. 6 is a schematic illustration of a landing stack coniiguration of this invention being utilized by eighteen aircraft;

Fig. 7 is a schematic illustration of a standard breakup procedure for a large formation of aircra'ftapproaching the stack configuration of Fig. 2;

Fig. 8 is a front elevation of a portion of the information panel and monitor board;

Fig. 9 is a front elevation of a portion of the emergency board;

Figs. 10A, 10B and 10C are illustrations of an .aircrafts instrument panel as the aircraft 4is located in various positions relative to the synchronizedstack;

Fig. llA is a simplified schematic diagram in block form of a communication system for use with the traftic controlsystem ofthis. invention;

Fig. 11B is a simplified schematic diagram in block form of a trafc control stack computer;

Fig. 11C is a schematic illustration .of an alternate stack configuration for use by two types of'planes having different ight characteristics; n

Fig. 12 is a schematic illustration partly in section of the stack vassignment mechanism for use in the 't'raiiic control computer;

Fig. 13 is a Afront lelevational view of the azimuth meter associated Ywith the mechanism for use in Vthe traiiic control computer;

Fig. 13A is a graphical illustration explaining `the operation of the clutches shown in Fig. 12;

Fig. 14 is a schematic diagram of a detail of the slot assignment mechanism shown in Fig. 12; and

Fig. l5 is a schematic diagram of the guard circuit for use withv the slot assignment mechanism of Fig. 12.

Although this invention is described for use with a ship-borne landing system it should be understood that its-application is not limited to use with an aircraft carrier, but that it can be utilized in conjunction with any shore base airport or landing strip.

The landing and tratiic control system ofthis invention is based upon an airplane landing stack configuration synchronized with a regular landing interval although it can be'4 readily appreciated that the traflic control system is adaptable to any predetermined flight path configuration. Referring to Fig. 1, it lis seen that this stack 21 consists of aV spiral pattern centered about an aircraft carrier 22 and synchronized with a predetermined regular landing interval. As described hereinafter, aircraft are controlled from an approach gate 23 at some distance from the'carrier such that they reach a previously assigned position in the synchronized stack 21 as shown by airplane 24 approaching stack position Q or airplane 25 approaching stack position A. Each aircraft in the stack has a common rate ofdescent of 500 feet per minute. In addition, the aircraft are spaced on the periphery of the helix or stack such that a 30-second interval exists between aircraft. 'One stack arrangement' may have a helix radius ofapproxirnately 3.2 nautical miles and, therefore, for a. Sil-second` landing interval, and a flying speed of 120 k'ln`0ts,vthe horizontal distance between aircraft will be 9 one nautical mile. For a rate of descent of 500 feet per minute the vertical separation between the aircraft will be 250 feet. All aircraft in the traic pattern continuously receive navigational information which insures their correct position. This information, in addition to being displayed in the cockpit of the aircraft, can be used to actuate the automatic pilot to produce varying rates of speed, turns to the right or to the left,` or vchanges in the rate of descent. y

The aircraft are admitted to the synchronized stack in the following manner. Assuming the aircraft in the stack are ying at aspeed of 1 20 knots and` the stack has a radius ,of'3.2 miles, the aircraft makes a complete turn about the carrier 22 every 10 minutes; Any aircraft desir- Ving to enter this stack pattern alerts the equipment on the ship when it enters the approach gate 23 which is at a distance of approximately 50 miles. A computer hereinafter described prescribes Ithe Acourse and speedfor the I until it intercepts the landing gate.

aircraft requesting entry into the stack 21 'in such,a mannery that the aircraft will arrive at a previously assigned spot inthe helix without any danger of collision. Obviously any spot in the helix can be filled at a chosen time if the speed of the aircraft is controlled.

The range of speed control necessary for 1the assumed stackl configuration is such that the ying time from the gate 23 to the stack 21 becomes a minimum` of 10 minutes,. the time necessary -for one stack position to make a complete rotation about the carrier 22, or a maxiinum of almost 20 minutes, the time necessary'for a stack position to make 2 revolutions about the carrier 22, fromthe mile approach gate 23 to the helix or stack 21. If we assume that an aircraft is capable of speeds up to 310v knots and has a stalling velocity of not more than 80 knots andif such an aircraft must c'over'the approach distancev from the gate 23 tothe helix I21 in 10 minutes, which would :indicate that the nearest stack position has been assigned to it, it will approach the Acarrier 22 at a rate of 280 knots. At the other extreme',

where an airplane mustcover the distance from the apy proach gate 23 to the helix 21 in 20 minutes the aircraft has an average closure rate of 140 knots. These velocities are, of course, relative to the carrier 22, and `therefore an additional margin of speed must be allowed.

Assuming the carrier velocity, or the combination of f wind and the carrier velocity, to be 30 knots, the range of velocities ,that the airplanes utilizing this landing system must be capable of obtaining varies from 310 knots `ata maximum to a minimum of 110 knots. These speeds, under the assumed conditions, are well within the capabilities of present-day aircraft. It is of course realized that the velocities mentioned above are taken merely as examples and can be modified as required to fit actual operating conditions. As hereinafter explained all of the above control signals, commands and information are producedautomatically and are not in any way determinedmanuallym 4necessarily-occupy theV complete periphery of the stack 21. Each aircraft will ily just that portion of the helix necessary for it to get aft of the ship at which point the landing leg 26 is entered. In a normal landing operation, all aircraft will normally approach the carrier 22 from the same direction because of the necessity for proper identification by ight over an outlying destroyer. Assuming that this direction of approach is over'thebow the aircraft proceed in the helix around the port sideto the stern and then enterthe-landing. leg.26. Hence'for this approach direction, .aircraft would never physically occupy the stack on the starboard side even, though all the positions or slots are assigned. Thus', if only a'portion of the helix shown inFig. 41 isA utilized as explained above, it is possible that the arrangement of carriers in a lleet can be managed such that the stacks of adjacent carriers vare I,non-interfering and so ythat certain lanes could be kept clean of trahi j' Based 'on the assumption that'the' landingitraic is organized asdescribed above, anindividual aircraft arriving by a prescribed route'` in the vicinity `of the aircraft carrier requires the cooperation 'of two systems on board i the carrier for completenavigation, traic control and landing'. The rst system must b'ring the aircraftffrorn or moremiles into the vicinity of lthe carrier 22 and feed the aircraft into the synchronized stack21. Theaircraft then orbits in the synchronized stack 21 x At this point of transition the navigational signalsnof the rst system cease andthe aircraft must `receive 'the landingsignals necessary to complete, the landing of fthe airplane. The signals necessaryfrom" each system, 'may `be, automatically 'switched `when the aircraft inteceptsthe landing gate 27. The 1vsecond :system orlandingfjequipment must provide they aircraft with C localizer, v localizary heading, glide slope and DME (distance measnringjequipmen information necessary to guide it onthe'landingleg 26. 'Ihe' com` plete path including the fsynchronizedprbiting will therefore be own in a pattern similarto the standard curved approach now used with manual operations.

For purposes of illustration.hypothetical landing problems are hereinafter illustrated and 4the `action of the signals on the aircraft control is described; The stack configuration and various assumed parameters such as aircraftspeed, jstackiradius, allowable separations and rates yof descent, may be revised 'as ynecessitated by actual operational requirements and the illustrations are provided merely to explain'the proposed 'principle of operation'only, the versatility' of'ths invention allowing a wide latitude in the choice ofparameters. Referring to Fig. 2, a plan view of a synchronized 'stack '21 at aparticular instant of time'is illustrated. The hypothetical slots or aircraft positions waiting to receive aircraft are lettered AI through S with slots E1 and E2 designated as emergency slots. The emergency slots are not lled during normal operation but are reserved for aircraft in trouble, thereby eliminating to a large extent the necessity for ever stopping" the stack with its associated loss of time or of delaying the landing of emergency aircraft.

, It is' assumedv that the stack rotates at the rate of one revolution every4 l0 minutesvand has a radius of 3.2 nautical miles,`thus corresponding to a time of 30 seconds between slots. The instantaneous altitudes of each slot are shown in Fig. 2. Thirty seconds after the instant illustrated in Fig. 2, for example, slot A.would be at an altitude of 1000 feet; slot B at 1250 feet, etc.,.thereby the helical path of the stack has a rate of descentof 500 feet a minute. It should be noted that slots P through S have two altitudes noted for them. The higher altitude is termed the entry altitude for theslot. For instance, an aircraft requestingentry from an azimuth of 306 would be commanded to enter at 5500 feet and ily slightly more than one complete revolution inthe stack beforeentering tl'itrlandingagate.at approxniately-250feetat'an azimuth-t off290 Ifthefaiiplaneiwashallowed'-to'enter:at"the =500i foot-altitude; the time? in thelstaclt' would be'flesszfthan 30y secondsgwhi'eh maybe insufficient forgood synchronization: Thusg. thef shortestftime allowedinv the.. assumed' stack configuration of Fig: 21 correspondstor-entryfintotslot/v A-fromf,0?azimuth andiisaboutlz minutesfin length-.1y Y The radiusifoffthe' stack is determinedtv byvv the tdesired" average' sp'eedi of: the aircraft'v in 'the' stack, and". as' wes assumelthe: desired'kavera'ge speed of'fthe'- aircraft t'ofbel 1.20linottu1the:` radiusfof the stackl issetat'?3.2-nautical It is obvi-vd oustliat onerevolutionfofa full st'ac'le:wouldcontaitrr20v aircraft? (incl'nding'two emergencies) t around? itstperiph-y ery and-that the 'aircraft'` are separatedinL altitude'fby'250 feet andiin' horizontal? distance byfone mile;

In a=similarrnanner-a secondL revolution offthestackl can; be*- formedl above 2 they first one` and in; synchronismf with'fit; A1 secondslot Ain-rthe'sameazimuthal direction; asA, but at an altitude of 6250 feet can be .:reatecl:` Slots.:y Af' through'fS v-p1. ogress; a's tins the -irstfstackutofarr altitude off. 15120001 feet: Thus, ani additional 20rairplanes canbe admitted to the upper fstacki andfprogressismoothlyf down two' turns'lofE thefhelixfto thef landinggate-27:I Ofcourse, thi'sa uppen staclef isfiutlized l only"y whenfsaturaton condi-v tionsf exist; that is; whenfraircraftfrequestf landingfclearance arf-lessI thany the 30secondf average intervalsia Normally, the: lower stach releasesxlan emptytfsloti every:30 secondsl andtthefupperf st'ackfis not utilized?iflandingrequest intervals averagesnotllesstthan-30 fseconds'z- Assuming for purposes of explanationthatfa large-:group oft' aircraft ar'eireturninggtoithe carrier, theifollowingdescribes'the: assignment-of. stack L'positions to otherindividualiy aircraftiv It is assumed-forfpurposesmfr explanationithaty theraircraft are'receivingfDMEandlomnimange informa tieni and.a are-telemetering backf tofthe carrier theiry posi,` tionsfin` distance, azimuth, elevation andftlieirfidentifica?l tions. Inka'ddition, itisia'ssumedfthat theaircraft`l receive telemeteredl commands in'y distance; azimuth and eleva-l tioncausing the y'autopilots to directth'e' aircr'aftf'toI the: commanded? locations Aircraft-maybe' assumedi tokarrive singly or inv groups, at random Itimes andfrom many di rections; Although-this type offoperationais'iseldom-i eneI countered on aircraft carriers; itis likely to'occur' at' shore bases'forf which purposes-the equipment is: equally suited;`

A- gate=23 is established at 50 nauticalmiles-ffi'om the: carrierV vat which pointv the Yautomatic control f commences.` Prior:v to the first airplane requesting p'errnission'-y to land; thezsynchronized stacl' i'squiescent; that-is; thefe'xactiposi# tion =of thee slotsfis; not' yet determinedz' f Referring to Fig; 3 assur'nerthatl aircraftIlias:reached the approach'gate 50 nauticalfmilestfrom thecan'i'erz", at an alfitudeof 5,000" feet andv at" an azimuth fof-",` have.

ingpreviously-requestedV or having been vcommandetltorhist'azimutli-z must bei constantI` at*09,A which enablesv to maintain homingY from thatdirection.v Hisftdecrease inv altitude'must'-move at some maximum requiredrate` to lreduce-his altitude fromL 5,000'F-feet1at 50 nauticalmiles to the' 1250 feet which1is-his1assignedentry altitude at 3.2 nautical miles from the carriercZZ. It is'not 'necessaryfto allow:f for windorrmovement'. of the carrier, since thesig# nalsoriginate from theicarrierl and are',vtherefore, relative` tofit; Essentially; thefmovementofthe carrier 22'is being;

continuouslyand? automatically represented in the 't telemetered command signallandthe aircraft 1 makes .continuall' correctionsnv inibis@ rate offclosure yin order toreach the.Y

designatedpoint at'the prescribed' time.

Let us *y assume that 30 seconds after aircraftVV 1 estab-- lishes the stack 21, aircraft 2 reaches the 50mile`approach gate at Van azimuth off 162" andy aty an= altitude 1 of 6,000

feet asf shownin Fig.f4l-` Since'f30second'sfhave'elapsedl sin'cezthe initiation off" the staclc 21 thefslotrpositionsfin tliestack have-rotated the equivalenti ofoneslot in 301 seconds: Aircraft Z'v sassigned slot Kfand` is given theV landinginstructionsI and" 11/2- minutes after aircrafty 14 initiated the' stack 21lla1: group' of three aircraft 3, 4 and 5 in closeiffrmation reachthe-504mile`approach gate 2 at an azimuth of 54 and at an altitude of 8000 feet, as

shown in Fig.' 5. The requests for a` slot in the syn chronized stack 211 from the three aircraft 3, 4 and 5 are received at'very close' intervals-and "af guard circuit onthe computer; as hereinafterv described prevents two aircraft, even if"callingjsimultaneously; from' being-assigned the same' slot. Th'eproperA assignmentforI each 'aircraft in thev group ismade4 almost instantaneously so that negligion=the^carrier 22 either manually or automaticallyv` with equipmentl well-known' 'to' those skilled in the: The telemetered Asignal on the carrierl 22 receivedf from the air craft 1, indicating that the first aircraft has reached lvthe 50-mile"approach gate, p urt's'fthe stack'computer `into op'- eration as hereinafter described, and"establisheszthestack as4 shown inFig. 2. Essentially aircraft'v l' isi-given azslot straight a'head, after whichA the stackf rotation isfstarted Assumingthat the described' speedof: the aircraft.' in' the stack'isA 120 knots, the `radius of the stack-is32 nauticalxmiles and the timefor'a complete rotation of thev stack j isy l0 minutes, the aircraft 1 must bemade to' ti'yfrom" its present positionat the approach gate 23v totthe'stack 21 at 3.2 nauticalmilesfrom the carrier`22 itr'exactlyA 1'0V minutes ,if he is assigned slot" A, andslofA makesone-` complete revolution ink 10 minutes;v Therefore, theaircraft 1 is "commanded by signalsfrom thek shipjto cover.:A

46.8 nautical miles iin 10 minutes; The aircrafts. throttle and possibly flaps rmay,` be controlled` to ,t adjust hisy speed ble timeeiapsesbef-ore each aircraft=gets`1andingjinstruc tions;` In; theJ case ofi larger close" formations a break-up procedure is` suggested'y beforel intercepting the 50mile gateI and thisV procedure is-'hereinafter described. The

first rof thegroup'of three aircraft, aircraft 3, isl assigned slot G, given a 10-minute elapse time to enter the stack as described for aircraft 1 and` aircraft'Z, and aircraft 3 is, commanded to descend to 2,000 feetwhich is the entry altitudeffor slot .GL For the second plane ofithegroup, aircraft'ztither computer, searches for`the next: availablev yslot vin a clockwise direction andjwould' therefore assign' s1'ot.H'.' This elapsed time, however', must be' l0 minutes'v andl 30'- seconds so that slot H will' b'e atv azimuth 54 n whenaircraft14approachesthe stack, and this necessitatesv that aircrafti move at. a slower rateth'anl aircraft 3 so thatthe46-8` miles'fbe coveredin 10"minut'es and 30 'sec Aircraft 4 isalso commanded to descend 2,000

onds. feet-since slot H will be at thatlaltitude when itisv intercepted at. an azimuth of 54.. The last' aircraftV of the altitude of. slot'I at 54azimuth. When these commandsV are received aboardthe aircraftin thegroup, the three aircraft in close formation begin to pull away from ea'ch other untilsthey assume the 30-second intervals: between them as dictatedby the command signals.

In this manner, the stack 21' keeps accepting aircraft to a maximum of 18 per stack, refusing entry to emergencyslots Ei and E2'. Itshould be pointed out that any' aircraft' in vtrouble can be givenl the first available slot, not'necessarily El ory Emifit requests landing permission atany time when the stack isnotlled. Therefore, it isf quite'possible that the* 18` aircraft` mentioned' above already 'cont'ain someVVV emergencies which 'have been 'han- Hence, itwill be the/slowest moving aircraft:

AircraftS will also be asked dled inhthe most expeditious manner. They are'being' broughtin tfor `a landing'inV the best possible time, as is every other aircraft within the-limits of the system and without disturbing normal traffic ow. Using two stacks, 40 `aircraft can be accommodated, including four `emergencies, witha-slot releasedfor an additional aircraft every `30 seconds. IfH the system is required to handle more than thisnumber of aircraft at a given time or at a greater rate, itis., possible y to direct the overflow tratlic into concentric orbits at the highest altitude of they stack, forming a mushroom traic pattern. HAS slots are released and reappear at the top of the stack the `fmushrooming aircraft already lat` the correct altitude are cleared `into successive inner orbits and nallyenter the stack at 30-second` intervals. e V

For purposes of. the above explanation convenient intervals of timeand azimuthgwere chosen and it should be,l ofl course,.u`nderstood that nthe system operates with any intermediateV combination of time or azimuth. For. ex

ample, consider the situation illustrated in Fig. 6 wherein;

the stack is filled with-airplanes 1 through 17 with `the exception of slot O and the emergency slots E1 and E2. At thetime aircraftlS requests landing permission the slots may be assumed to bein the intermediate positions shown, and aircraft .18 is assumed to be at an azimuth of 96 when it enters the 50mi1e approach gate 23. In searching for an open spot clockwise the computer traverses 348 `before it locates empty slot O. The amount of elapsed time, therefore, to the stack for airplane 18 is Neglecting wind or the motion Vof the carrier, the average speed of the aircraft would be such as to cover 46.8 miles in 19.67` minutes or 142,8 knots. In reality the 142.8 knots represents the rate of closure between the carrier 21 and the aircraft 18` and `this is the rate at which `the airplane must be commanded to y. yAssume `the carrier to be steaming at a heading of 96 such as to maintain a 30- knot wind across its landing deck. Then the actual in dicatedlanding speed of aircraft 18 would be 112.8 knots. The assigned entry altitude forJ 96 azimuth would be 19 minutes `Inmcomputing. the maximum `speed that an aircraft a' the minimurrntime, namely, 10 minutes. His ra'te of closure is, therefore,` 46.8 miles in 10 vminutes or 281 knots. Assume the carrier to be steaming directly away r from the aircraft at an equivalent of 30 knots and then the indicated air speed would be 311 knots and represents the maximum `required speed of any aircraftunder thev above assumed conditions.

.Thefforegoing examples include the assignment into the stack of aircraft arriving singly,` or in small groups from various azimuths and `at different times. Any pra'c`- tical equipment must be capable of handling a large group of aircraftarriving ina Itight formation. Since the DME accuracy "hf known equipment isof the order of 11000 feet, as "faras the computer is concerned, all ,aircraft in a closeuflight `appear to be at the same point. The computer would then proceed to assign a slot to each aircraft, but yat random,` thereby allowing the possibility of an aircraft in the rear of the squadron being assigned an early slot." This would meanthat the aircraft would have to overtake and pass members of the squadron in front of him with the subsequent danger of collision. It is preferable therefore that large formationsbreak up before .l

intercepting the e-mile approach gate 23 so that the aircraft enter the gate individually, either at slightly diie/1'` ent razimuths or with at least a 1,000-foot spacing between aircraftor both. In the event of foul weather, dispersion in .f any, ease, it isdesirable thai: a, standard brcakup `.pro-

cedure vbe ladopted ybefore interception of Lthe 50-mile gate,

the carrier the.` group leader orders` a standard break-up procedure. ..The first A'group or lead ight 29 of four aircraft 1' `through` 4' continues oncourse. The second group 30.of;.four aircraft 5f through 8'turns 30 to the right. and Lafter 30 seconds` resumes` the toriginal heading whilethe. third, group 31- of, four 'aircraft 9' through 12' performs the s amemaneuver tothe left. Finally the fourth group 32of aircraftl through` 16' would turn 603.10 the-.right andtafter Oneminute-resume the original heading. ,"Ihismaneuver is? shown in the` enlarged insert 33'0f Flgalfn t', .11" t.

f g Once; each @group isclear,the.group leader calls for an ,echelon toxthe-.right formation,- andthe aircraft rearrange themselves as shown'in theenlarged insert 34 at 60 miles. Individualiaircraft then begin `to pullI away from `the aircraftim front. until at least 1,000 `and preferably 2,000`

feet distance exist between members of the Hight as shown in Ltheenlarged;insert 3 5wat 50miles... vAt 50 miles the` computenaboardthe `aircraft carrier 22 begins to` make stack .l assignnzlents.` and i because of t the distribution both` .putedlniay'fnot,necessarily `assign slots in order to each` l,I Ilernl?$21".'ofoneilightf However, because of theA spacing,

no conflicting upaths `canfoccur.` For .purposes of illus-` tration,fffitl isassumed;that;the computer` assigns slots 'alternately tggmembers of thegsecond r:and third ights 30 and lfflalssigning 'slots F through M. Finally, Amembers' jofl.the,fourth ight 32 are assigned slots N through Q. flu'lhe, ircraftj` arenowarranged on the approach at llvlsecond; ntervalsexcept for one-minute intervals` between ,airraf wand 5 an d airerafts 13 and 14'. These one-minute"intervalswcorrespond to the emergency slots dint they clovetailfv with their asy i 'ig'ht continues in the stack tide f ,the carril and lto the landing gate-apdfdnall Lmt'ogthc landing legas Yshown in Fig. 1. It should "qbeiioted, that-thegaircraft do not actually occupy @arremete Qt thc sack to the starboard of the carrierfor'gthisrarrangement ofeeapproach, 4direction and @carrier eadling@Y `should alsofbeenoticed that the lead aircrafitl'.t ofjtheformationz flies `the most direct route position to the carrier 22.I addition, this lead aircraft 1". Hwillfalways receive [the `earliest assignment, assuming thefstack tolbe'ulbfy, 'calling forthe rriaxiniluml approach speed, and it isthusibbvious that the leadiaircarft is landed intt'hefbest possibletime. HOther members ofthe formationl occupyprogressive :iQ-second intervals behind, thelead` aircraft (except for the two emergency` intervals) `andfwit follows that the ,complete squadron is landed lwithino losse of time `due to the standard breakup procedre'oi'any'other cause. e l

i The stacki assignments yand command information supplied 'to the `aircraft is ldetermined onboard the carrier 22cby` meansI `of'fa synchronized. 'stack e computer. It should again, ybexpointed out, `that the communication ,the (ll-mile gate after` position toa the-1 carrier.. Thi A .izepotteclsr information:l may bei displayedzonLaniinformationpanel 36 associated witlr the.' computer, a; portionr-'of whichv shown` in Fig.. 8.

Each, vertical; columnrdisplaysz all informationl associated with. a*` single aircraft# Asueach aircraftiis identified its' identification numberisidisplayed in. a: window'A 37 and the. vertical column'. then.; assigned" to. that particular aircraft. They threev meters. 385.39.v and- 40 display the aircrafts' reported azimuth,.. distance and.; altitude-` re-v spectively; From; this informationg. a computer; assigned t to each.aircraft, assigns a slot positionin thestack. and causes.: the-r telemetering.. ofy command signals to the aircraft to be.-initiated;so1thatf the aircraft .flies the; pre-V scribed course. As hereinafter: described: the computer for each aircraftfmay be part oftheazimuth indicator 38 which comprises a =ro'w foflightsf* 42h-46: deiining: the4 approximate: position; and. state; off thel aircraft relativer to.

termine-the landing order of. the variousaircraft.. The .landing order is displayed in window'47l at the bottom of the column. If4 desiredthev slot assignment A through S may be displayed in place ofl orA in additiontothe landing. order.

When the-aircraftreachesfthe stack 21, 3.2 nautical.

miles from carrierv 22, light. 43V is lit` indicating thatk the aircraft is orbitingA about the ship in its-assigned slot.

Light 44is turned on when the aircraft reaches: the landinggate 27: andison the-linallanding leg'. Incase it: is necessary to'. prevent the/landing1 of an aircraft for. any. reasonavmanual wave-off switch. 48 isprovided so that a particular aircraft or slotumay be. cleared from the traic patternat any timebyv the operator. If an aircraft isA waved-off for any. reason, either manually or automatically light 45 is turned on.y Finally anv alarm light 46 is associated with each aircraftdenoting that the aircraft is: notresponding to the computer signals. This alarm information is .derived in the apparatus by a. continuous comparison of. the reported'positions of the aircraft with the commanded. position. determinedby the computer.` The alarm light 46` may also. control an automatic. wave-otf.

The monitor board 41 maybe-remoted to vother parts of `thecarrier 22such as.on deck or to afcontrol center. If.remoted the :monitor board' 41 must? include aircraft identification means Suchas shoWnby-window 37 ofethe information panel 36;

Associated with the information panel 36 and-the monslot position of the landing stackv 21. As each slot position A through S isA assigned to-an aircraft by thecomf puter the top light 50 in the slot column is switched on and signifies that the slotis reserved' for the particular aircraft whose identification number is displayed in window'51. In the vertical columnsv assigned to the emergency slot .positions Eland E2 the emergency board containsthe control button 52 forman'ually releasing. the emergency slots so that they will accept the aircraft in trouble. A stack stop control button. 53 is` provided for the initiationof a vstack stop for. purposes hereinafter described. Each` vertical column also provides an .ad

vance button 54 which could beusedinstead of a waveofto clear any` particular slot. Advancing aslot. back-s;

and may. thereforetb'e: contained-on the-information panel t Below therinformation l panel; 36:: is .ray monitor boardz41'.

up; all computers.behindltherselectedsloti byfoneiposition,

thus; clearing the selected slot..

operating with the. traic controlsysternof this.l invention.

the SO-mile.` approach gate,l.landing.control signalsstart beinggreceivedandf theiautopilot or pilotis directed to'` follow themto arriveathisassigned stack position at ther correct: time, .azimuth and altitude. TheA fbugsf ori cornmandindicators on the instruments beginz to operate withtheir rates of movement being determined by the'. stacl;L

computer aboard the carrier and the information radioed tothe aircraft via the `communication equipment.`

For purposes of illustration assume thataaircraft'l of,y

Figure 6 has. reached the approach gate 23.V Referring tothe aircrafts .instrument panel illustratedin Fig.. 10A` the air vspeed indicator 55 shows'that the plane is travelling..-l

at 112.5 knots atan azimuth of 96'e as shownby the deflection fromthe required course.A Should aircraft. 18: vary from this. azimuth as would bte-indicated bythe azimuthneedle 59,.the aircraft is turned right or leftas.

required. The deection. of the crosspointer indicator 58 and thus. the right-left control: forv thek autopilot, is. determined by the interval between the bearing indicator` needle 59 and the bearing-command bug57. The present` elevation of. aircraft 18 is indicated by the pointed- 60 ofthe altimeter 61 and the altitude commandI bug 62 indicates the stack entry kaltitude of.2,583 feet.' The rate of climb (or descent) shown on meter 63 isdetermined by` the. interval between the altitude pointer. 60.and1the altitude. command bug 62 ofmeter 61 and at some maximum prescribed rate.

The distance of'. aircraft 18 tothe. carrier 22 isshown bythe pointer 64 of distance meter 65. Since. it was@ determined, as heretofore explained, that'aircraftLlS: must u proceed at aclosure rate of 142.8v knots to'arriveatits -slot positionO at the correcttime, the distance command:l bugy 6.6 startsfto-decrease. atthe 142.8 knOLcloSurevrate;4 The air speed indication displayed on meter55..iside;-. termined by the interval.r between the' distancercommand:

bug 66-and the`distance=pointer 64 onmeter 65. Thus it is.. apparent that the interval between the--pointers-.and

command bugs of. bearingmeter 56, altimeter 61 and. distancemeter .controlthe movements of. the-aircraft... to cause it. to. approach the stack on a predetermined` course.r

controlled as explained above. Shortly beforeI reaching. the predetermined 3.2 mile radiusstack the distance indication is used to trigger the autopilotinto apreseribed.

right. turn designed to prevent over-shooting asthe stack is approached and to bring thev planel intoA itsI assigned slot. asymptotically. In addition, the speed'` is: reduced ftom.the'assigned approach` speed of 142.8'knots to"-the It is assumed that the aircraft has completed. its.V mission. andV a homingtcourse wastaken and thexautopilotv engaged. When within: rangesf of the carrier: the. aircraft eitherv requests permisssion 0r is commanded; to. land.; Fig.A 10Ay is anv illustration of the: aircraft's' instrument? panel as; it reaches. the 50rnile approach., gate 23. s It'y should be clearly understood that they illustrations. of.. an` aircraftis instrument panel 4as it. reaches the 50mile1ap. proach. gate23; It should be clearly understood'that: the. illustrations of an aircrafts instrument panel. are for` purposes of explanation only and no. attempt. ismad'e to portrayl the optimumv or actual. instrumentation. At.`

'path along the carriers course. l`'crafts receiving equipment is switched to the localizer and stack speed of 120 knots. Since the aircraft must Know* orbit about .the carrier 22 in theV stack 21 the bearing bug 57aof bearing meter" 56a rotates in synchronism with the synchronized stack rate of 360 in l0 minutes. If thelazimuth `needle 59a lags the bug 57a, power is ap plied to speed up the aircraft and therefore catch up to the slot position. Conversely, speed is reduced if the needle 59a leads bug 57a. The distance command bug 66a of Adistancelmeter 65a remains constant at 3.2 miles which is `the radius of the stack 21. Should the indicated 'distance from` 3.2 miles the aircraft will bank-right or left to correctuthefdrift. The altitude command bug 62a of altimeter 61a moves at the rate of 500 feet a minute descent. speed will be 120 knots, in order to follow the 30` knot motionof the carrier it will be necessary for the aircraft to fly as fast as lSOlknots or as slowas 90 knots when flying parallel to the course of the carrier.

' Fig. `10C illustrates the aircrafts instrument panel as the aircraft 183 enters the landing gate 27 which is located at a point port of the ships stern the plane leaves the stack 21 and enters the landing leg 26. This action is triggeredby shipborne computer when the correct azimuth indication, 290"y in the illustrated example, is coexistent with the 1' correct altitude, approximately 250 feet. At this point the aircraft executes a prescribed left turn such that its path becomes nearly tangent to the landing Simultaneously the airglide path signals. A timing mechanism is started such that if the localizer and glide path ag alarms do not disappear vinra given time (15 seconds) an automatic wave-off results. Excluding this possibility the localizer and'glideslope signals control the plane. In addition, from the localizer equipment, localizer heading information is being received which aids the autopilot in the asymptotic approach and acts as a monitor on the localizer course. AThe control of the autopilot by the localizer and glide slope is performed in the normal manner controlling the left-right motion and rate of descent respectively. `T he air speedrmeter `55h indicates a predetermined optimum approach speed. The deflections of the crosspointer indicator 58b are controlledby the localizer and glide slope paths. The rate of climb displayed on meter 63h is determined by the glide slope deliection and rate. The altimeter 61b is controlled by the glide slope signal as its bug 62bis inactivated. l

After.1 proceeding to the stern of the ship `a cut signal, as hereinafter described, determines whether the altitude of the aircraft, particularly its heading, is within certain limits safe for landing. If not, a wave-0E is initiated. The

cut-signal shutsidown the power and the aircraft lands on deckand is arrested inthe usual manner.

As heretofore explained, both a stack computer and a communication system are essential to the operation of the traiclcontrol system of-this invention. It is the function of'the computer, once an aircraft has requested orfbeen ordered to land, to define the aircrafts position in distance, azimuth and altitude as a function of time and relative to the stack configuration and to telemeter these coordinates to the aircraft via the communication equipment during the approach and stack procedures. Sincethese coordinates are being telemetered continuously as a function of time, it is obvious that information as to speed,.rate of `turn or bank, and rates of climb or descent are available. Each aircraft is assigned a single computer which goes into operation as determined by the aircraft's identification. The computers are operated in banks with the necessary mechanical and electrical connections between them and could be mounted as part of the information panel shown in Fig. 8.

r Referring to Fig. 11A, a simplified `schematic diagram' in blockform of a communication system 68, 69a for use in conjunctionwith the trac control system 69 of this invention `is shown. One embodiment of a communication It must be remembered that while the average Paul R. Adams and Robert LlColin, Serial No. 38.6,57-4, filedr October 16, 1953, .for Aircraft Radio Navigation Systemf now U. S. 4Pater`1t..No. 2,836,815,` and assigned to the samelassignee asthis application.

Essentially the communication system comprises a rnobile transmitter-receiver unit 68which is located aboard the aircraft and `a transmitter-receiver unit 69a forming ak fixedstation 69` located aboard the.` carrier or at any other trafccontrol centen` The mobile `unit equipment 68 transmits signals, preferably pulse coded,which are indicative of its identity and position coordinates includingfdistance,` azimuth and `altitude as well asan alert or precursorsignalto indicate that an aircraft is about to transmit. GT-he fixed stationntransmitter 69a transmits signals `from which the craft may determine its position aswell as address signals to indicate to which plane the following command signals are intended. The radio com-I munication link between the carrierr and aircraft comprising the fixed station transmitter-receiver equipment 69a and the airborne transmitter receiver equipment 68 exchange dall the necessary information for the proper operation of thetratic system.:

Normally the fixed station r69-will be able to receive the signals transmittedfby.theaircraft before the aircraft .reaches vthe mile radius designatedas the ap proach gate 23 but in any event the computer commences operation when an aircraftreaches the approach gate 23. However, provision made so that aircraft may be permitted entry tofthisy region even if they do not desire to land,` such as t when flying ycover for the carrier in which case the computer portion must be' preventedfrom operating;y Hence a distinct precursor signal is used to alert the shipborneiequipmentl. The alert signal is transmitted bythe mobile equipment 68, prior to other signals, when the pilot requests or is commanded to land. The transmissions ofthe `mobile unit 68 are detected in the receiver portion. ofequipment 69a and coupledto alert circuit` 70. c Circuit "70 decodes and recognizes the alert signal and causes a signal to be coupled to gate.71*t`hus opening gatet71 and `permitting the signals following the alert signal to be coupled t0 the identification portion of the system.

In most situations, such as when used aboard an aircraft carrier, 'the traiiic control system of thisr invention will be cooperating `with two groups of aircraft.` The first group` of'aircraft` includes all those planes which are permanently'assigned to the carrier and will use the traflc control system most` often'. Each of the planes in the first group can be permanently assigned tocooperate With a particular computer. Thus iflplane 3000 permanently assigned `to `the aircraftcai'rier., transmits an alert signalfollowed by its encoded identification signal.. The detected alert signal causes gate 171 tolopen and the identification signal is coupled .to the identication circuits 72a,;;72b, 7211,:7211 and72i. MIdentication circuit 72a recognizesrthe identification signal of plane 3000 and `causes gate* 73a tonopen. identification circuits 72b, 72n, 72p t and 72j fail to recognize the identification signal` of plane 3000 and thus no signals4 are coupled to gates 73h or 7Bn, or finder circuit 74p.or 74j.l p 1 I y .l

VThe identification` signals passed by circuit 72a are coupled via line 375e to computer 75a which is assigned to plane 3000 and are'displayed on a plane identification 37 shown in Fig. 8L `Simultaneously gate `73a:` permits the position report signals, which follow the identification signals, to be coupled to computer 76a via line 77a.

As hereinafter'explained the computer 76a determines the necessary command signals to causeplane` 3000 to y al selected *flight path. The command signals from the computer"76a assignedto plane Y3000 are coupled Via line-78a to aA modulator 79 whose output is encoded and transmitted t `by l the shipborne transmitter-receiver The other` 113 equipment 69a.x Of course provision may be'made for transmitting addressv signals fromeach computer, in any event it is necessary for each. planete know which command signals are intended for it. v

The second group ofplaues, with which the traffic. controlv system of this invention must cooperate, may be termed visiting planes. rObviously each plane must be assigned a computer which vwill commandy the plane to y paths within its capabilities. All aircraft. maybe classified into typical types according to its character-A istics. A visiting plane requesting permission'vor commanded to land will. transmit an alert signal whichis detected'in circuit 70 whose output opens gate 71. Y The address of the visiting craft will contain signals `indicative of its type and these signals will be identified by an identification circuit such as 72p or 72j. When identi fication circuit 72p recognizes an address as coming from a plane of vtype .P the signals-are passed to a finder circuit 74p whose function itis to hunt or find a computer which can cooperate with, a plane of type P that is not presently assigned to another aircraft. When an empty computer is found by circuit 74p the identification signals are coupled to an identification circuit 72p which decodes the signals and couples them to the computer 76p via line 75p. Simultaneously the circuit 72p causes gatel 73p to openl coupling the posi-- tion report signals, which follow the identification signals, to the computer 76p whose output is coupled to modulator 79 in a manner similar to .theoutput of computer It is obvious that each aircraft utilizing the traffic control system of this invention wil-l-be assigned a computer which is designed in. accordance with the flight characteristicsof the particular plane. However it is possible that the stack configurations heretofore described will not be suitable for all types of planes. For example assume that a ight of jet propelled aircraft request permission, to land. It is .possible that jet aircraft could notr ily slow enough to maintain-their assigned slot position. Referring to Fig. 110 an alternate. stack conf figuration is therein shown which is suitable for use by at least two types of aircraft having Widely varying ight characteristics. The1stack pattern comprisestwo helices having different radii. They type of aircraft having. the capability of flying at high speeds are assigned to the outer helix While the slower aircraft are assigned tothe inner helix. The landing rate of planes can be maintained at a predetermined interval and the exact distance of thev radius of the outer or inner helix can oe determined from the ight characteristic of the aircraft. type. .f

' Referring. to Fig. 11B=a schematic diagram in block form of one'embodiment ofthis invention isy thereinv shown.y .As the identification circuit 72a recognizes the assigned plane 3000 identication signals they are passedI to plane displayl 37 via line 75a. The signal is also passed .to trip mechanism 80. The output of the trip mechanism S puts the stack. assignment. mechanism 81 into operation Whose function it is to search for an empty slot position in the stack 21 and upon finding one assign it to theaircraft associated with the computer.

Thedistance, azimuth and altitude indicators 74, 7S and.76 shownI in Fig. 11B may be the same instruments as are mounted on the information panel shown in Fig. 8. The position report signals passed. by` gate 73a. are coupled to the position .distance decoder 82a, position azimuthdecoder SZb fand position altitude decoder 82C.

The outputv of the decoder circuits 82a, 82h and 82e,

decoder circuits 82a, 82h and v82C tothe stack assign ment mechanism 81.

As hereinafter explained, knowing the aircrafts lazi muth. and the-positionofv the assignedslot, Vthe stack assignment mechanism. 81. then-sets. the time function for distance, azimuth and altitude for the aircraft' to follow morder for it.to become synchronized into the stack. When the actual distance of the aircraft is 50 miles from thecarrier, needle 77 'of distance-meter '713 makes contact with ,the 50-.mile approach gate trigger 83 which couples a. signal to the switching circuits S4 which then. allows the telemetered command signals t0- be passedv to the modulator 79 and requipment 69 for transmission to the aircraft. The commandA signals from switching circuits 84 are lalsoicoupled to the command distance decoder 85a, command azimuth decoder 85h and command altitude decoder 85e whose output control the positioning of the command position indicators 86a, Sb and 36e on meters 74, 75 and 76 respectively. Thus both command and actual position indications are available at meters :'74, 75 and 76.

Remembering.V the stack procedure hereinbefore described, the time. functions for the necessary command signals' are ,derived as fol-lows: Y

(l) The distance function is derived from the angular interval between. the aircrafts` azimuth and the. assigned slot at the time of assignment;

(2) The azimuth function consists of holding the azimuth at the time of assignmentl throughout the approach phase; andv (3). The altitude functions consist of correcting to the entry altitude whichis kdetermined from the aircrafts azimuth'. 1

The `distance function circuit 87 is driven through a variable speed device 88 and definesthe desired position of the aircraft with respect to timefrom the approach gate 23 to thel stackZlv at 3.2 miles fromthe carrier.. Once cuits 84 to modulator 79-tol modulate the transmitter portion of equipment 69..'

The aircraft is. allowedl to'V approachl the stack! underk the above conditionsuntil'justprior to reachingthe stack radius distance of 3.2 miles-the actual distance needle 77 makes contact with .the pre-stack trigger`91 causing a signal to be coupled to.- the. stack, entrybank signal cir cuit 92. TheA output; of .circuit-v 92 .causes the plane to maneuver in a manner heretofore described ljust'- prior to its entry into the stack.

As the plane arrivesatthestack radius distance of k3.2. miles needle 77 contactsthe stack trigger 93 and a new f set of functions are telern'eteredV to the aircraft: (1) VThe distance function holds'y the aircraft at radius of the stack; v

(2) The azimuth function. holds the-aircraft in its assigned slot position; and- (3) The altitude function defines a' l500v foot-per-minutev descent fory 'the aircraft;

The stack azimuth function circuit 94 and the stack altitude function circuitf95l defines the coordinates for the aircraft while in the stack 21 and up to the landing gate`27. The signal' from the stack trigger-93 is vutilized to switch the outputv of switching circuits 84 from the approach function circuitsI to the stack function circuits. For monitoring purposes, the differential between the actual position pointers 77, 78 and 79 andneedlesv 86a,

86h and 86e indicating thefcomrnanded` position of the aircraft arer continuously' measured andif the' interval exceeds'l a predeterminedI limit, indicatingr that the aircraft is not responding to the command signals, an alarm is given and an automatic wave-olf is initiated.`

The landing gate 27, as described previously, is a point from which the aircraft leave the stack 21 and begin the landing leg 26. The landing gate 27 is not fixed in space, hence it must be referred to the carrier. This information is obtained from the ships gyrocompass heading 96 which positions the landing gate azimuth trigger 97. Although the aircraft azimuth position needle 78 may contact trigger 97 more than once, the aircraft must also be at a predetermined altitude as determined by a1- titude position needle 79 contacting the landing gate altitude trigger 97a beforea signal is coupled to the stack release signal circuit 98 the output of which clears the stack assignment mechanism 81 and may also switch the aircraft receiver to the landing system signals.

Referring to Figs. 12,` 13 and 14 an embodiment of portions of the computer including the stack assignment mechanism 81 for use in the traffic control system of this invention is shown. The mechanism `of the drawings can be an integral part of the azimuth indicator 38 and can therefore be contained in the information panel shown in Fig.`8. It is assumed for purposes of explanation that the position coordinates are defined by potentiometers. One stack assignment mechanism 81 is associated with each computer and therefore with an individual aircraft. In addition to the azimuth indicating needle 99, the unit contains on its face 100 a ring 101 of twenty slot detining contacts A through S, one for each slot position in the stack 21, and a contact brush 102. The ring n 101 and hence the slot defining contacts A through S are rotated at the stack speed of one revolution per minute by a master stack motor drive shafty 103. The shaft 103 drives all computers from a common power source thereby insuring that all computers remain in synchronism. The slot contacts A through S are coupled to contacts a1 through s1 in a stationary terminal board 104 through slip rings a2 through s2 mounted on armature 105. The slip rings are coupled to the terminal board 104 by means of brushes 106.

At all `times while the aircraft is in the air and within range of the carrier equipment, the azimuth servo 113 is positioning the azimuthindicator 99 in accordance with the telemetered azimuth report of the planes position. TheA azimuth servo 113 controls meter 38 by coupling its output through shaft 114 viagears 115 to shaft 116 on which the azimuth indicator needle 99 isa mounted. During this period and when the airplane alert signal is coupled to the computer, clutches 107, 109 and 110 are engaged, the `other clutches 108,` 111 and 112 being disengaged. Since clutch -107 is -engagedthe azimuth servo113 drives the contact brush motor y117 through gears 118a and 118b of gear train 118. The contact brush motor 117` drives the contact brush `102 through shaft 119 `via gears 120 to shaft 121 on which the contact brush 102 is mounted. This causes the contact brush 102 to maintain alignment with `the indicator needle 99 of azimuth meter 38. Sinceclutches 110 and 109 are also engaged the stack azimuth potentiometer 122 and the approach azimuth potentiometer `123 are both driven by the azimuth servo 113 and therefore are kept intrack. In jaddition theV stack altitude potentiometer 124 is tracking the stack azimuth potentiometer `122 and the approach altitude potentiometer 125 is always defining the entry altitude `for the indicated azimuth.

As the aircraft enters the SO-mile approach gate 23,` the trigger, signal, hereinbefore explained, causes clutches 110 and 112 to engage and all the other clutches 107,` 108, 109 and 111 will be disengaged.

that the stack slot assignment is made. The disengaging of `clutch 109 leaves the approach azimuth potentiometer 123 defining the azimuth of the aircraft as it enters the approach gate 23 and the approach altitude potentiometer 125 is defining` the stack entry altitude for It is at this time` that azimuth. At this time thecontact brush motor 117 starts to run, driving the contact brush 102 clockwise away 4from the indicated `azimuth and around the slot defining contacts A through S. The brush 102 will stop at the first slot that is not assigned, as hereinafter described. The rotation of the Contact brush motor 117 also `causes the stack azimuth potentiometer 122 and stack altitude potentiometer 124 to rotate by transmiting power through shaft 126 and gears 118a and 118b of gear train 118 and through clutch 110 which is engaged. Potentiometers 122 and 124 define the azimuth and altitude of the assigned slot at the moment when brush 102 makes the assignment. 'In addition, the motion of the brush motor 117` causes the ratio changing shaft 127 of the variable speed drive 128 to set the proper ratio between the drive input shaft 129 and the drive output shaft 130; t p p When the contact 'brush 102 locates an empty slot it triggers a new clutch arrangement such that clutches 108, and 111 are engaged while clutches 107, 109 and 112 are disengaged. This `clutch arrangement causes the master stack motor drive shaft103 to drive the stack assignment mechanism through gears 131, shaft 132, clutch 108 and gear train 118. t The distance potentiometer 133, having been preset at fifty miles, isthen turned by power transmitted through the variable speed drive 128 and clutch`111 which is engaged so as to dene the correct rate of closure for the aircraft to the stack. In addition the stack altitude potentiometer 124 and the stack azimuth potentiometer 122 are driven synchronously because clutch 110 is engaged and they continuously define the coordinates of the lassignedslot position. All this time, it must be remembered, thatthe aircraft is being given telemetered command signals derived from the distance potentiometer 133 and from the approach altitude and azimuth potentiometers and 123. During this clutch arrangement the contact brush 102 is driven synchronously with the ring 101 so that it will remain on and rotate with an associated slot defining Contact, always permitting a usual check.

The above conditions remain xed until the pre-stack trigger 91 shownv on the distance meter 74 of Fig. 11B is reached by indicator needle 77. At this time a unique signal, the stack entry bank signal, is momentarily telemetered, putting the aircraft into a predetermined bank designed to prevent overshoot on entering the stack. Simultaneously the aircrafts speed is adjusted to the stack speed. f

Seconds later the aircraft arrives at the 3.2 mile radius of the stack and at this point clutch 111 disengages leaving the distance potentiometer 133 fixed att 3.2l miles. Simultaneously thesource of the telemetered command signals is switched from the approach azimuth and altitude potentiometers 123 and 125 to the stack azimuth and altitude potentiometers 122 and 124. If the aircraft has responded properly the two sets of potentiometers 123, 125 and 122, 124 will be defining the same coordinates at the time of switching and hence no discontinuity results. The stack potentiometers 122 and 124 are rotated synchronously from the time of slot assignment and now de` ne to the aircraft the azimuthal position of the slot and the altitude at each constant of time, causing the aircraft to ily the helical path of the stack 23 with a rat of descent of 500 feet per minute.V

The landing gate triggers 97 and 97a, placed on the periphery of the azimuth and altitude meters 75 and 76 shown in Fig. 11C is servo positioned from the` ships gyro heading such that it maintains a point 20 to port of the stern of the carrier. When the landing gate triggers 97 and 97a simultaneously make contact with position needles 78 and 79 a unique release signal is telemetered to the aircraft. The release signal causes the aircraft to bank into the landing leg 26 and automatically switches the aircraft receiver equipment to the landing system transmissions. .At the same time the release signal clears and resets the computer and it is no longer assigned.

Referring to Fig. 14, a schematic diagram of a detail of the slot assignment mechanism 81 is shown. Referring again to the time when the computer makes the slot assignment, that is when the aircraft enters the 50-mile approach gate 23 and a reservation is desired a switch 134 is closed by the approach gate trigger signal Voltage, from power source 135, is then applied through a guard circuit 136, hereinafter described, via switch 137 of relay 138, to the contact brush motor 117. The contact brush 102 then wipes around the contacts A" through S" until a short circuit is encountered, as is shown for slot contact A, where the contact is shorted to ground through relay 139. Now current ows through the coil 140 of relay 138 and the coil 141 of relay 139. The current ow in coil 140 causes switch 137 to open, stopping the rotation of the contact brush 102 because the power to the brush motor 117 is removed. Simultaneously, the current in coil 141 causes thecontacts of switch 142 to open which prevents any other Contact brush in any other stack from being shorted to .ground when it is coupled to slot contact A and therefore indicates that slot A is assigned. Relay 143 shows the position of the relay switch when the slot S has been assigned to an aircraft. It must be remembered that there is a relay 143 similar to relay 139 for each slot contact and all the relays for each slot are interconnected as indicated by lines 144 and 145.

Referring to emergency slot contacts E1" and E2 an additional switch 146 is added to the relay circuit 147. Relay 147 is similar to relays 139 and 143 and all other relays associated with the slot contacts A" through S. Switch 146 is normally opened, thereby preventing the contact brush 102 from coming to rest or assigning slot E1 and holding slot E1 of the stack in reverse. Slot E1" may be released to an aircraft in trouble by closing switch 146, either manually or automatically by some predetermined unique emergency signal, after which slot El can be assigned.

Referring to Fig. 15 a schematic diagram of the guard circuit 136 is shown which prevents two aircraft, when calling simultaneously, from being given the samer slot assignment. A fast stepping relay or continuously rotating commutator 148 is utilized in conjunction with a stepping relay actuator or commutator motor 149 which rotates armature 150 around the contacts of 148. One contact of 148 is associated with each computer of the system. The contacts of 148 are each coupled through switch 137 to the contact brush motors 117 of each computer. Obviously if only one contact brush motor 117 is allowed to rotate at a time, the same slot assignments cannot be given to two airplanes which call in simultaneously. The 50-mi1e approach gate trigger signal causes switch 134 of the computer corresponding to the aircraft identication to close. When the commutator armature 150 comes around to the contact of 148 coupled to the operative brush motor 117 current flows in the coil 151 of relay 152 and power from source 135 is coupled to the motor 117 through switch 137. As current flows through coil 151 of relay 152 it causes the normally closed contacts of switch 153 to open decoupling the commutator motor 149 from the power source 135 and causing armature 150 to cease rotating. The armature 150 is halted in this position until the computer has found a reservation (as explained supra) at which time the brush motor switch 137 opens. When switchv 137 opens brush motor 117 stops rotating and current ceases to flow in coil 1,51 of relay 152 closing switch 153. The armature 150 will then continue to rotate in search of another computer desiring to make a slot assignment to an aircraft.

In the event that it is necessary to establish a second landing stack configuration above the first stack the computer should be altered. If after once rotating around indicates that the slot the slot defining contacts the brush 102 cannotznd an 75 empty` slot, a second set of assignment relays,represent ing the upper stack, are switched in. The brush 102 then continues to rotate searching for an empty slot in the upper stack. In such a case it 1s also necessary to simultaneously switch altitude potentiometers defining the upper stack or make the potentiometers used cover the` complate range. In this manner, perfect synchronism is obtained for both turns if the helical stack and smooth passage down the complete path is assured.

While I have described above the principles of my invention in connection with specitic apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation tothe scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A traffic control system, having a base station for cooperating with a plurality of mobile units each of said mobile units including communication means for reporting its position coordinates to said base station, comprising a plurality of slot assignment mechanisms one assigned to each of said mobile units, means to control said mechanisms in synchronism to establish a predetermined traflc control pattern having a plurality of slot assignments each of said slots representing a location in space and having varying position coordinates, means to compare the position coordinates of one of said mobile units with the varying position coordinates of a slot assignment, means to determine necessary command signals for controlling movement of said one mobile unit to cause position coordinates of said mobile unit to coincide with said varying slot position coordinates at a predetermined time and means to communicate said command signals to said mobile unit.

2. A traffic control system according to claim l wherein said base station further includes interlocking means between said plurality of slot assigning mechanisms to prevent more than one of said mobile units being assigned the same slot assignment by more than one of said slot assignment mechanisms.

3. A traffic control system, for cooperation with a m bile craft having communication apparatus for reporting its position, for establishing the course said craft must follow to be integrated into a predetermined traiiic pattern having a plurality of moving slot assignments each of said slots representing a location in space and having identifying slot position coordinates varying with said movement, comprising means for establishing said pattern of moving slot assignments including identifying position coordinates for each slot, means to assign one of said slot positions in said pattern to said craft,means to compare the position coordinates of said craft with the position coordinates of said slot and means to determine the path coordinates said craft must follow to cause said slot coordinates and said craft position coordinates to coincide at a predetermined time.

4. A traic control system for a predetermined area for guiding mobile craft having communication apparatus for reporting its position coordinates to a base station having communication equipment for communicating to said craft command signals indicative of a course for said craft, comprising means at said station for establishing a traffic pattern having a plurality of moving slot assignments each of said slots representing a location in space and having slot position coordinates varying with said movement, means to assign one of said slot positions inlsaid pattern to said craft when said mobile craft enters said predetermined area, means to compare the position coordinates of said craft with the position coordinates of said assigned slot and means to determine the path coordinates said craft must follow to cause saidslot co ordinates and said craft position coordinates to coincide at a predetermined time. l 5. A tratc control system for a predeterminedarea for guiding craft having communication apparatus for,

'i9 feporting its position Coordinates to a base station having communication equipment for communicating to said craft command signals indicative of a course for said craft comprising means at said station for establishing a trat'lic pattern having a plurality of moving slot assignments each of said slots representing a location in space and having slot position coordinates varying with said movement, means to assign one of said slotpositions in said pattern to said craft when said mobile craft enters said predetermined area, means to compare the reported position coordinates of said craft with the position coordinates of said assigned slot, means to determine the path coordinates said craft must follow to cause said slot coordinates and said craft position coordinates to coincide at a predetermined time, means responsive to said coincidence of coordinates to cause said command signals communicated to said craft to be indicative of said varying' slot assignment coordinates.

6. A traic control system according to claim wherein Asaid means responsive to said coincidence of coordinates further includes means anticipating said coincidence to cause said craft to follow a course which gradilally causes the position coordinates of said craft and said slot coordinates to become identical.

7. A flight path computer for determining the course of a craft, having radio communication apparatus for reporting its position, must follow to be integrated into a predetermined pattern having a plurality of moving slots each of said slots representing a location in space and having identifying slot position coordinates varying with said movement comprising means for establishing said pattern of moving slot assignments including identi- `fying position coordinates for each slot, means to assign one of said slot positions in said pattern to said craft, lmeans to compare said slot position coordinates with position of said craft, means responsive to said comparison to determine the time necessary for said 'slot position to assume the reported azimuth of said craft, means to determine the rate of change of the distance coordinate 'said craft must assume to cause said craft to intercept said slot after the elapse of said determined time, means to determine the altitude coordinate of said slot when intercepted by said craft after the elapse of said determined time, means to determine the rate of change of altitude coordinate said craft must assume to cause said craft to intercept said slot after the elapse of said determined time, means to determine the azimuth coordinate said craft must follow to intercept said slot after the elapse of said determined time and means to communicate said coordinates to said craft.

8. A ight path computer for determining the course of a craft, having radio communication apparatus for reporting its position, must follow to be integrated into a predetermined pattern having a plurality of moving slots each of said slots representing a location in space and having identifying slot position coordinates varying with said movement comprising means for establishing said pattern of moving slot assignments including identifying position coordinates for each slot, means to assign one of said slot positions in said path to said craft, means to determine the time necessary for said slot position to assume the reported azimuth of said craft, means to establish signals indicative of rate of change of distance, means to select one of said rate of change of distance signals responsive to the reported distance of said craft and said determined time, means to establish signals indicative of azimuth, means to select one of said azimuths signals responsive to the reported azimuth of said crafty and the azimuth said assigned slot assumes after the elapse of said determined time, means to establish signals indicaiii/ e of altitude, means to select one of said altitude signais responsive to the altitude of said assigned slot after the elapse of said determined time and means to cornmunicate said selected rate of change of distance, azimuth and altitude signals to said craft.

9. A computer for determining the course a craft, having radio communication apparatus for reporting its position coordinates, must follow to be integrated in a predetermined moving traffic pattern having a plurality of positions, each of said positions having identifying position coordinates varying with said movement, comprising means for establishing said pattern of moving slot assignments including identifying position coordinates for each slot, means to assign one of said positions in said pattern to said craft, means to compare the reported position coordinates of said craft with the coordinates of said assigned position, means to determine the necessary command signals for controlling movement of said craft to cause said crafts position coordinates to correspond to said assigned position coordinates and means to communicate said command signals to said crraft.

10. A landing path computer for determining the course craft, having radio communication apparatus for reporting their position, must follow to be integrated into a predetermined landing pattern having a plurality of moving slots each of said slots representing a location in space and having identifying slot coordinates varying with said movement forming a stack pattern comprising a plurality of stack assignment mechanisms to establish said pattern, means to assign one of said plurality of stack assignment mechanisms to each of said craft, each of said stack assignment mechanisms having means to assign an individual slot position to its assigned craft, dependent upon the reported position of said craft, means to communicate to said craft the varying slot coordinates of its assigned slot and means aboard said craft responsive to said communicated coordinates to cause said craft to assume a position wherein the coordinates of said craft equal the coordinates of said slot. l

l1. A landing path computer for determining the course craft, having radio communication apparatus for reporting their position, must follow to be integrated into a predetermined landing pattern having a plurality of moving slots each of said slots representing a location in space and having identifying slot coordinates varying with said movement forming a stack pattern comprising a plurality of slot assigned mechanisms one for each of said mobile units, means to control said mechanisms in synchronism to establish said landing pattern having a plurality of slot assignments each having varying position coordinates, means to assign one of said slots to said craft, means to communicate to said craft the distance, altitude and azimuth coordinates of said slot, means aboard said craft to cause said craft to move to the position of said communicated coordinates, means responsive to the coincidence of said slot coordinates and the reported position of said craft to cause said altitude coordinate to vary by a given rate of descent and said azimuth coordinate to vary as a function of time and to maintain said distance coordinate constant and means to communicate said coordinates to said craft.

l2. A landing path computer for determining the course craft, having radio communication apparatus for reporting their position, must follow to be integrated into a landing stack pattern having a plurality of slots each of said slots representing a location in space and having identifying slot coordinates comprising a plurality of stack assignment mechanisms, means to control said stacl assignment mechanisms in synchronism, means to assign one of said plurality of stack assignment mechanisms to each of said craft, each of said stack assignment mechanisms having means to assign an individual slot position to its assigned craft, means to communicate to said craft the distance, azimuth and altitude coordinates of its assigned slot, means to vary said altitude coordinate of said slot by a given rate of descent, means to vary said azimuth coordinate of said slot as a function of time and means to maintain said distance coordinate of said slot constant. 

